Diterpenoids from Acacia leucophloea

Phytochemistry,1980,Vol. 19, pp. 1979-1983.80 Pergamon Press Ltd. Printed in England.

DITERPENOIDS R. K.

BANSAL,* *

MARIA

C. GARC’bALVAREZ,1.

FROM KRISHNA

ACACIA C.

0031-9422/80/0901-1979 $02.00/O

LE UCOPHLOEA

JOSHI, * BENJAMIN RoDRiGUEZt

and

RENUKA

PATNI*

Department of Chemistry, University of Rajasthan, Jaipur-302004, India; t Instituto de Quimica OrgBnica, C.S.I.C., Juan de la Cierva 3, Madrid-6, Spain (Received 4 January 1980)

Key Word Index--Acacia

leucophloea; Mimosaceae; new pimar-8(14)-ene diterpenoids;

13CNMR data.

AbstractPFrom the root bark of Acacia Leucophloea (Mimosaceae) two new pimar-8(14)-ene diterpenoids have been isolated. Their structures have been established by chemical and spectroscopic means as lb,l5R.16-trihydroxypimar8(14)-ene(leucophleo1) and 15R,16-epoxy-lj?,l lr-dihydroxypimar-8(14)-ene(leucophleoxo1).

INTRODUCTION

leucophloea (Roxb.) Willd. is a tree very characteristic of the dry regions of India, and its gum is used in indigenous medicine. In previous work on this plant [l, 21, some known substances were characterized. A study ofthe root bark has now led to the isolation of two new diterpenoids whose structures were established as 1/3,15R,16-trihydroxypimar-8(14)-ene (1, leucophleol) and lSR-16-epoxy-lp,llcc-dihydroxypimar-8(14)-ene (2, leucophleoxol). Acacia

RESULTS The

AND DISCUSSION

first of the new diterpenoids, leucophleol (l), C,,,H3,0,, had an IR spectrum which showed strong hydroxyl(3290,3200 cm - ’) and olefinic (1655,840 cm - ‘) absorptions and no CO bands. The ‘H NMR spectrum of leucophleol showed signals for one olefinic proton without vicinal hydrogen atoms (1 H, singlet at 6 5.23, IV,,, = 4Hz), four protons geminal to hydroxyl groups (complex signal between 3.76 and 3.26) and four C -Me singlets (0.98,0.86,0.83 and 0.80), whereas its MS showed the base peak at m/e261 (loss of a -CHOHCH,OH fragment) and loss of water from the molecular and the m/e 261 peaks (m/e 304 and 243, respectively). Acetone-anhydrous CuSO, treatment of 1 yielded an acetonide derivative (3) which on acetylation gave compound 4. The ‘H NMR spectrum of 4 showed a 1H quartet (J,,. = 9, J,,, = 6Hz) at 6 4.66 assigned to the proton geminal to an equatorial acetoxyl group which must be placed between a tetrasubstituted sp3 carbon atom and a methylene grouping. The protons involved in the acetonide group (3 H) appeared as an ABC system between 3.98 and 3.54. All the above data suggested a diterpenic structure based on the pimarene or isopimarene skeleton for leucophleol with a 1,2_dihydroxyethyl side chain, a secondary (and equatorial) hydroxyl group at the C-l, C3 or C-12 position and a double bond between C-8 and C14. This last assumption was also supported by the fact that the ‘H NMR spectrum of 1 showed a clear signal for the C-7 allylic equatorial proton (6 2.29, brddd,

J = 14Hz, J,,, = 5, J,,. = 2 Hz, Jaliyiic‘v 1 Hz) identicii” with that observed in some isonimar-8(14)-ene \ I derivatives [3]. The ’3C NMR spectrum of the acetonide derivative (3) was in complete agreement with structure 1 for leucophleol (Table 1). The location of the carbocyclic hydroxyl group at the C-l equatorial position was supported mainly by the strong y-gauche effect (AS = - 6.4 ppm) shown by the C-20 carbon atom, and also by the fact that the chemical shifts of the C-l, C-2, C3, C-4, C-5, C-9, C-10 and C-11 carbon atoms in 3 were identical with the calculated values obtained from pimar8( 14)-enes [4] taking into account the introduction of an equatorial -OH group at the C-l position [5-71 (Table 1). On the other hand, the reported values of the C-8, C-l 2, C-13, C-14, C-15, C-16 and C-17 carbon resonances in 15R,16,18-trihydroxypimar-8(14)-ene (5) [8] are almost identical with the same carbon resonances calculated for leucophleol (1, Table 1) from the data of its derivative 3 and the observed effects caused by an acetohide group in several diterpenoids with a 1,2_dihydroxyethyl side chain (Rodriguez, B., unpublished results). In particular, the observed value for the C-8 carbon atom in 3 (138.6 ppm), which is not affected by the acetonide grouping (Rodriguez, B., unpublished results), pointed towards a pimar-8(14)-ene skeleton [4,8] and not its C-13 epimer [9]. The latter shows a C-8 carbon resonance at 136.5ppm and a possible deshielding d-effect on this carbon atom in 3, caused by the C-l hydroxyl group, may be discarded [lo]. The 13CNMR data also provided proof of the stereochemistry at C-15 in leucophleol; a 15R configuration showed the C-15 carbon resonance at 78.2 ppm [8], almost identical with the value calculated for compound 1 (79.1 ppm, see Table l), but very different from those reported for the 15s epimer (75.5 ppm) [8]. The absolute configuration of leucophleol (1) was established by the application of Horeau’s method [ll ] to compound 3 (see Experimental). The absolute stereochemistry of the equatorial C-l alcohol was 1R (lp-OH) and hence this new diterpenoid belongs to the normal series. The other new diterpenoid isolated from Acacia leucophloeu, leucophleoxol (2), had the formula 1979

R. K. BANSAL et (II.

1980

Table No.

Carbon

1. 13C NMR chemical 3

shifts in ppm relative to TMS Calc. for 1*

2 __-

1 2 3 4 5 6

7 8 9 10 11 12 13 14 15 16 17 18 19 20

79.1 d 29.9 tt 39.8 t 33.2 s 54.1 d 22.4 I 36.3 t 138.6s 52.0 d 43.9 s 21.8 I 31.8 tf 36.3 s 126.7d 83.4 d 65.6 t 21.7q: 33.2 q 22.7 r/z 8.5 q

79.1 30.9 39.x 33.3 54.3 22.9 36.0 138.3 51.7 43.7 21.9 31.8 37.4 t27.1 79.1 63.5 21.5 33.9 22.5 9.4

76.0 LI 28.1 f 39.8 f 33.1 s 55.1 dt 24.3 t 36.6 I 139.7 S 59.2 il 47.4 s 69.3 d 38.2 I 36.8 s 123.6 d 55.7 iii 44.x I 24.9 q 33.5 q 21.4y 12.4 ‘,

*Values for C-l to C-l 1 and C-18. C-19 and C-20 set refs. 14 ~7:: values for C-12 to C-17 calculated from 3 and ref. [9]. t. $.Values in any vertical column may be interchanged, but those given here are considered to be most likely.

C,,H,,O, and its IR spectrum showed absorptions for strong hydrogen-bonded hydroxyl groups (31 lOcm_ ‘) and for a trisubstituted olefinic double bond (1670. 865 cm- ‘). The ‘H NMR spectrum of 2 was very informative and showed signals for one olefinic proton (6 5.01) without vicinal protons (W,!, = 3 Hz), a pseudoaxial proton geminal to a secondary hydroxyl group (a five-line signal at 3.98) which may be placed in the C-l 1 position of a pimar-8( 14)-ene skeleton with the ring C in a distorted chair conformation (Jlla,sa = J, ,p,,2u = 5.5, J Ilp, ,2z = 11 Hz) [3], and another axial proton also geminal with another secondary hydroxyl group (3.55, J,,. = 8.5, J,,, = 6.5 Hz) which was placed between a tetrasubstituted .sp3 carbon atom and a methylene grouping as in leucophleol (1). In addition. the ‘H NMR spectrum of leucophleoxol (2) showed signals for a monosubstituted oxirane ring (lH, q, J, = 4.5, J2 = 2.5 Hz, at (52.79, and a 2H octet at 2.61), for the 7/G allylic proton (equatorial) in pimar-8(14)-enes (2.28, broad eight-line signal, JDem = 13 Hz, J,,. = 5, Jee. = 2, Jiiiyiic - 1 Hz), for the H-9 proton (2.03, br d, J 9a.l Ip = 5.5, J,l,iyiia = 1 Hz) (allylic and vicinal to the C11 hydroxyl group) [3] and finally. for four C-Me singlets at 1.04, 0.98, 0.86 and 0.82. Double resonance experiments confirmed the above assignments because on irradiation at 6 3.98 (H-l 1) the doublet at 2.03 (H-9) collapsed to a broad singlet, whereas irradiation on H-9 (2.03) caused a narrowing (WI ,z = I .5 Hz) of the olefinic proton signal (5.01) and transformed the quintuplet of the C-11 proton into a quartet (Jllp~lzp = 5.5Hz, Jllp,12a = 11Hz). On the other hand, the equatorial H-7 (p)proton was also coupled (allylic coupling) with the olefinic proton (irradiation at b 5.01 caused a narrowing of the signal at (32.28, and vice versa). All these data may be accommodated in structure 2 for leucophleoxol. in which

the low IR hydroxyl group absorption and the small J, lp,92 value (cidesupra)must be rationalized by a conformational change in ring C caused by 1fi-hydroxy and 1la-hydroxy interactions 131. Moreover. the 13C NMR spectrum of leucophleoxol (Table 1) showed carbon resonances in complete agreement with the proposed structure 2 and the differences with compound 3 must be rationalized by the additional 1 la-hydroxy [7. 12. 131 and the 15,16-oxirane [14] functions and also by the conformational change in ring C in the molecule of leucophleoxol (2). Al! the above assumptions. the configuration at C-l 5 of the oxirane ring and the absolute stereochemistry of the molecule of leucophleoxol (2) were confirmed as follows. Acetic anhydride- pyridine treatment of 2 yielded a diacetate (6). LiAlH, reduction of leucophleoxol gave a trio1 (7), the ‘H NMR spectrum ofwhich showed a typical pattern of a -C-CHOH -Me grouping (b 3.56, 1 H, q J = 6.5 Hz, H-15; 1.14. 3 H, rl. .I = 6.5Hz. 3H-16). Thus the presence of an oxirane ring in 2 was confirmed. Acetone-anhydrous CuSO, treatment of trio1 7 yielded an acetonide derivative (X) which was acetylated to give 9, the ‘H NMR spectrum ofwhich showed the H-15 quartet paramagnetically shifted (b4.79. .I = 6.5 Hz). Thus the acetonide formation occurred between the C-l and C-I 1 hydroxyl groups. On the other hand. CrO, pyridine oxidation of trio1 7 gave a mixture of two compounds easily separated on PLC. One of these compounds (less polar component) was the expected triketone 10 (no -OH absorption in its IR spectrum: a 3 H singlet at ii 2.20. 3 H-16: no protons geminal to hydroxyl groups) whereas the other one had structure I1 (hydroxyl group bands at 3590, 3450cm~‘; 63.75, 1 H, (/. J,, = 9 Hz, J,,,. = 6Hz. H-l) (see also Experimental). Treatment ofthc triketone (10) with oxalic

Diterpenoids from Acacia leucophloea

19 18

1981

R’ R* 7H H 8 -CMe,9 -CMe,-

R’

RZ R3 1H H H 3 H -CMe,4 AC --CMe,-

2

R’=R2=H

6

R’=R*=Ac

10 11

OH

R’ H H AC

R1,R2 = 0 R’ = OH: R2 = H

\ :,,ll\ Q’ 0

I 4

0

0

iI

5

acid in EtOH solution yielded an isomeric compound which possessed an a&unsaturated keto group UVi.EatH 242 nm (E 6700)] with a [IRv,,, 1663 cm-‘, tetrasubstituted olefinic double bond (no ‘HNMR signals below 6 3.5). Thus, structure 12 must be assigned to this compound which is in complete agreement with all the above deductions. Finally, application of the Horeau’s method [l 1 ] to compound 8 (see Experimental) defined the configuration of this centre as 15S, and hence as 15R the stereochemistry of the C-15-C-16 epoxide ring in leucophleoxol (2). The same procedure [ 111 applied to the C-l equatorial alcohol in compound 11 (see Experimental) established the absolute configuration of this function as 1R (lPOH), and thus leucophleoxol belongs to the normaI series as does leucophleol (1). EXPERIMENTAL

Mps were determined in a Kofler apparatus and are uncorr. ‘HNMR and 13CNMR spectra were measured at 100 and 25.2 MHz, respectively, in CDCI, soln with TMS as int. standard. Assignments of 13C chemical shifts were made with the aid of offresonance and noise-decoupled 13C NMR spectra. Elemental analyses were carried out in Madrid, with the help of an automatic analyser. Plant materials were collected in December

12

1977 from the out-skirts ofJaipur (India) and voucher specimens were deposited in Rajasthan University Botanical Laboratories (Herbarium Sheet No. 11342). Isolation of’the diterpenoids. Finely ground root bark of Acacia leucophloea (5kg) was extracted with C,H, and the extract coned. The brownish semi-solid obtained (100 g) was chromatographed on a Si gel (Merck, No. 7734) column (150g). Elution with C,H,-EtOAc (4: 1) gave leucophleoxol(2,450mg); further elution with C,H,-EtOAc (3: 1) yielded leucophleol(1,250mg). Leucophleol (1). Mp 1766178” (Me,CO-n-hexane); [a]? + 6.5” (~0.25, EtOH). IRv~~:crn~ I: 3290,3200,1655.1090, 1015.840. ‘H NMR: see Discussion. MS (70eV. direct inlet) m/e (rel. int.): 322 (M+, 0.6), 304 (0.8), 289 (I), 273 (2.5), 261 (100) 243 (46) 233 (6), 187 (14) 158 (14) 121 (57), 105 (62) 95 (70). 81 (56). [Found: C, 74.37; H, 10.69. C,,H3,0, requires: C. 74.49: H, 10.63Y0]. Leucophleoxof (2). Mp 185-187” (MeJO-n-hexane); [a]:,” - 131.0” (~0.28, EtOH). IRv~;cm~‘: 3110, 3070, 3005, 2840, 1670, 1064, 1050,880, 865, 828. ‘HNMR: see Discussion. ’% NMR: see Table 1. MS (75 eV, direct inlet) m/e (rel. int.): 320 (M+, 3) 305 (3), 302 (8) 287 (7), 284 (5) 271 (100) 269 (8) 257 (15) 119 (68), 105 (99), 91 (53) 81 (53) 69 (60) 55 (63), 43 (62). [Found: C, 74.95; H, 10.15. C,,H,,O, requires: C, 74.96; H, 10.06%]. Leucophleol acetonide (3). Leucophleol (1, 260mg) was dissolved in dry MezCO (80ml) and CuSO, (500mg) was added

1982

R. K. BANSAL PI cd.

to the soln. The mixture was heated under retlux for 12 hr. The reaction product 3 was crystallized from n-hexane. mp 61 63”; [+>” + 1.9” (~0.48, CHCI,). IRv>;;‘cm‘: 3490, 1660. 1220, 1170, 1070. 870,830. ‘HNMR: 65.30 (lH.hr.s,ni, L ==4Hz.H14) 3.96 3.38 (4H. 16 lines, H-l. H-15 and 7H-16). 2.28 (IH. hr ddd. J,,,” = 14.5.J,,. = 5, J,,. = 2.5,.J,,,i,,i, 1 1 Hz,/iH-7) 1.40 and 1.32 (3Heach,s,acetonide),C-_Mesingletsat 1.01.0.86.0.83 and 0.81, 13C NMR: see Table 1. MS (75 eV. direct inlet) ILIAC (rel. int.): 362 (M+. 1.5). 347 (3). 329 (1.5) 304 (2). 287 (5). 369 (5). 261 (loo), 243 (45). 121 (571, 105 (65). 101 (771, 95 (75). 81 (54). [Found: C. 76.28: H, 10.49. CZ2H,,0, requires. C. 76.19: H. 10.57”,]. Application (g Horrtrir’.~ rnefhod [l 1] 103. A mixture of ( f )-xphenylbutyric anhydride (0.43 mmol) and 3 (0.055 mmol) in Py soln (3ml) was kept at room temp. for 16hr. x, = +0.363: IK. !x> = +0.2X2. %I ~ 1.1~~ = +0.053. Confgurdtion Ace@ deriratire 4. The hydroxyacetonide 3 (54m.g) was acetylated in the usual manner yielding 4 (53mg): mp 127- 129” (MeOH); [Y]:’ + 30.7” (~0.14, CHCI,). IRr~~:crn~ i: 1730. 1660.1250.1165.1070,1030,X70.830. ‘HNMR): n5.?4(lH.hr:, I+,, 1 = 4Hz, H-14) 3.66 (IH, y, .J<,o,= 9Hz, J,,,. = 6Hz, H-l). 3.9X3.54 (3H. ABC system. H-15 and ZH-16). 2.03 (3H. s. -OAc), 1.41 and 1.33 (3H each. .s, acetonide). (‘-Me singlets at 1.02,0.92,0.88and0.86. MS (70eV.direct inletIrn,‘c~(rel. int.): 404 (M’. 0.3). 389 (0.7). 346 (0.5). 344 (0.2) 329 (1.31, 303 (IX). 30’ (11).269(71.261(3),243(100).1-‘7(4).111(2?).101 (97).X1 (28). [Found: C, 74.33. H. 10.03. CL,H,,,O, requires: C. 74.21: H, 9.97”,,1. Leirc~~ph/rw~o/ tliocetc~e (6). Treatment of 2 ( IOmg) with Ac,O Py m the usual manner gave the diacetatr 6, a syrup. ;%I: + 17.2 (~0.40. CHCI,). IR v~;~‘crn~ ‘. 1725, 1250, 850. ‘H NMR:ii5.13(2H,complexsignal,H-14andH-l1).4.56(1 H, Y>J,., = IO. Jo, = 4H7. H-l 1. 2.74-2.43 (3H. ni. H-15 and ZH16) 2.00 (6H. 5, two -OAc), C-Me singlets at l.OY (6H) and 0.87 (6H). LiAIH, reducrion Q/ lencophleoxol to yield trio/ 7. Compound 2 (120mg) in Et20 soln (30ml) was reduced with LiAlH, (200mg) at room temp. for 1 hr and gave 7 (118 mg). Mp 196 198” [I];’ ~ 93.9” (<,0.37. MeOH ) (Me2C0 n-hexane): lRv~~:crn~ ‘: 3320.3200, iO95,1060.910. X80. ‘H NMR: ii 5.14 (lH,hrs. l#‘,L = 5Hz. H-14),4.19 (IH, ,ii. It’, 2 = lXHz, H-11). 3.56 (lH, 4. J = 65Hz, H-15). 3.59 (lH, y. J,,. = 9. J,,,. = 6Hz. H-l ). 1.14 (3H. d. J = 6.5 Hz, 3H-lh), C-Me singlets at 0.99. 0.96, 0.86 and 0.82. MS (75eV. direct inlet) we (rel. int.): 322 (M&,0.4), 304(0.7). 289 (0.7), 277 (36). 259 (44). 241 (39). 145 (43) 131 (37). 123 (801, 105 (loo), 95 (34), 81 (34), 69 (48). [Found: C. 74.68; H. 10.71. CzoH,,O, requires: C. 74.49: H. 10.63”,,]. Acrtonidc 8. Trio1 7 (90mg) was treated as previously described for I, yielding 90mg of the hydroxyacetonide 8. Mp 110 112” (Me,CO- fi-hexane); [z],‘,” - 32.4” (c.O.54, CHCI,). IRrkt:crn ‘, 3300. 1665. 1215. 1170. 1085, 920. X85. 880. 870. X55. ‘HNMR: ci 5.13 (IH, hr s, Lf(,, = 5Hz, H-14) 4.35 (1H. X lines, brddd. JI,4.sz = 12. .J,,B.,2z = 6.5. J ,,,,,, zg = 4.5. J ,,,,%,,< 2 1 Hz, H-l I). 3.57 (2H, complex signal. H-l and H-15). 2.31 (lH, hrddd. J,,,,, = 14, J,,f,f,li = 5, .I ,,,, hl = 2. .J,,,l,,, = 1 Hz. equatorial H-7). 1.71 (1H. d, J = 12H1, with small allplic coupling, H-9) 1.44 (6H. .s, acetonide), 1.14 (3H. d, J = 6.5 Hr, 3H-16). C-Me singlets at 1.02. 0.94, 0.86 and 0.X3. MS (75 eV. direct inlet) m:r~ (rel. int.)’ M+ absent. 317 (M f -- CHOHCH, side chain, 57) 304 (2). 300 (3), 287 (2), 259 (100). 241 (70). 145 (48). 119 (45). 109 (65). 105 (87). 81 (63), 69 (48). [Found: C, 76.24; H, 10.6% C,,H,,O, requires: C. 76.19: H. 10,57”,,j. Application of Horeuu’s rnrthod [I I ] lo 8. A mixture of ( + l-xphenylbutyric anhydride (0.43 mmol) and 8 (0.066 mmol) in Py soln (2 ml) was kept at room temp. foi- 20 hr. Y, = -0.600:

Configuration 15s (for ?, = -0.403: r, - 1.1 zz = -0.157. leucophleoxol 2, 15R). Awtyl ucefonide drricutiw 9. Obtained from 8 (3Omg) in the usual manner. 9 (20mg) had mp 117 119” (MeOH). _ 71‘3- 68.2” (cO.33. CHCI,). IR $y;crn i : 3030. 1737. 1240. tr:,, 1095. X85. X60. X20. ‘H NMR ((3): 5.13 (1H. hr\. I+; z = 4H/. HHIS). 3.32 (1H. ttltl. 14). 4.79 (1H. ‘,. .I -h.SHr. J I ip.91= 12.5Hz, Ji,,,lrz= 7Hr. .I,,,j,,zs= 5Hz. H-11) 3.56 (IH. q. J,z,z,l = IOHz. J,,,zz = 6.5 HT. H-l), 231 (1H. hrtldd. J,,,-, = 13Hz. Jqp,60 = 5Hz. J-,,,, = ?H,, .I. ,j,, 1 z 1 H7. equatorial H-7) 2.00 (3H. \. +Ac). 1.68 (lff. hrri. .I = 12.5 Hz. I 15 (3H. il. = 1 Hz, H-9). 1.44 (6H. ,s. acetonidc), J >,iyi>i J = 6.5 Hz. 3H-16~. C-Mc singlets at 1.00. 0.98. 0.86 and 0.X3. MS (75 eV. direct inlet) IWL’ (ml. int.): 403 (M +. 0.3). 389 (0.4). 344 (0.6).317(38).269(8).259(100),741 (56).18714X). 159 (33). I45 (53) 119 (42), 109 (53). 105 (80). 81 (6X). 69 (351. _Found. C. 74.36: H. 10.04. CzsH,,,O, requires: C. 74.21. H. 9.97”<,]. Trikrtorw IO md h?,dro~!,di~etoric 1 I. To a suspension of CrO, (300mg) in Py (3 ml) was added trioi 7 (45 mg) in Py soln (3 ml). The mixture was left 24 hr at room temp. The soln was diluted with Hz0 and extra&d with EtLO. The Et,0 extract \\a, di-icd and evapd, The residue was a mixture of two compounds which were easily separated by PLC‘ on Si gel plates de\elopcd with CHCI, MeOH (19: I ), ‘fiiiketow 10 (I 6 mg. less polar- component): mp97 100” (MeOH): [r]l’,“+- 7X.7 (cO.16. CHCI,). iH NMR:ci5.79 IR I,“!” cm ‘: 17OO(strong). llOO.Y55.875.X40. In.,% (IH, hrs, M’,,2 = 5H7. H-14). 3.40 (II-I. hr\. Ii; J = 5H/. H-9). 2.20 (3H. 5. 3H-16). (‘-Me smgletc at 1.24. 1.13. 1.10 and 0.92. MS(75eV.directinlet)r~r,e(rel.1nt.):7I6(M~.5),301(2).287(~~~. 273 (70). 255 (18). 161 (47). 121 (44). 113 (X6). 95 144). 33 (100). [Found: C. 75.87, H. 9.03. C,,,HI,O, requires: C. 75.91. H. 8.92”,,]. H!,r/ro\-~dihrrorlp I I (12.7mg. most polar cvmponent ): (MelCO -ii-hexane). [xjfy ~ 217.7” (cO.i?l. mp147 149 CHCI,). IR ,;I::,,, ‘. 3595. 3350. 1715. 1690. 1287. 1140. 1050. 1040. 980. 865. ‘HNMR: ~$5.53 (11-1. hr\. It’, L = ~Hz. H-14). = ~WL,H-l).7.05(?H.a.?tl-16~. 3.75(1H.q.J,.,z,, = 9Hz.J,,,, C-Me singlets at 1.35. 1.03. 0.89 and 0.85. MS (75eV. direct inlet)m;e (ml. int.): 318 (M -.O.h). 303 (1). 300 (O.-l), 275 (36). 257 (31 I. 161 (35), 147 (40), 135 (i2). I23 (54). 121 (100). 69 (29). 43 (36). [Found: C. 75.61: H. 9.46. C20H~o0,~ requires: C, 75.43: H. 9.50?,,]. 4pplic’rrfion ol Horutrrr‘\ rnr~iiod II 1 ] 10Il. A mixture of ( + i-xphenylbutyric anhydride (0.12 mmol) and 11 (0.036mmol) in Py soln (Iml) was kept at room temp. for 20 hr. x, -= -0.404: IR. x, = -0.458: 3, - l.Irz = f0.100. Configuration o/‘lO 10 p’vxi~w 12. Compound IO Douhk bond i.\onlrri_~rtiorl (9mg) and oxalic acid (3mg) (n EtOH soln (5 ml) were heated under reflux for 24 hr. The solvent was evapd and the residue wa\ chromatographed on a TLC aluminium sheet of Si gel 60 l“zjl (Merck.Art. 5554)elutedwith EtOA L ii-hrxane (I : 1) yielding 12 (6mg): mp 137- 138” (EtOAc n-hrxane): [r]:,” + 6X.1’ (cO.066. ’ 1703 hr. 1660. 1630 (double bond). 1300. CHCI,). IR vi’::crn I 112. 1030, 1006, 965. 8YO. 735. iH NMR: (i2.26 (3H. \. 3H-lb). C-Me singlets at 1.58. 1.15. I.12 and 0.02. L(V ,.bZ:” nm (I )’ 212 (67001. MS (75eV. direct inlet) vi t’(rel. int.). 316 (M ‘. 40). 301 (6),273(89).260(41),2551?6).241-(161.232~7).117151i).1Y’~(45~. 175 (74). 161 (64). 147 (40). 113(771.13 (1001. [Found: C. 76.04: H, X.91. C,,,HI,O, reqmres: C, 75.91: FJ, X.92”,,: Ack,lowledgc,nzr,~ts We thank Miss M. Casado and Miss M. Plaza (Madrid) for recording the ‘H and “C NMR spectra and Mr. J. Prieto (Madrid) for elemental analysts. This worh was supported m port by the Spanish Commisihn Asesora de Investigation C‘ientifica y Tecnica and in part by the Council of Scientific and Industrial Research. Nen Delhi. India.

Diterpenoids

from Acacia

REFERENCES 1. Mukherjee, S. K. and Murty, V. V. S. (1952) J. Sci. Ind. Res. Sect. B, llB, 125. 2. Joshi, K. C. and Sharma, T. (1977) J. Ind. Chem. Sot. 54,649. 3. Bohlmann, F. and Lonitz, M. (1978) Chem. Ber. 111, 843. 4. Wenkert, E. and Buckwalter, B. L. (1972) J. Am. Gem. Sot. 94, 4367. 5. Gonzalez, A. G., Arteaga, J. M., Bretbn, J. L. and Fraga, B. M. (1977) Phytochemistry 16, 107. 6. von Carstenn-Lichterfelde, C., Pascual, C., Rabanal, R. M., Rodriguez, B. and Valverde, S. (1977) Tetrahedron 33, 1989. 7. Eggert, H., VanAntwerp, C. L., Bhacca, N. S. and Djerassi, C. (1976) J. Org. Chem. 41, 71.

leucophloea

1983

8. Wenkert, E., Ceccherelli, P., Raju, M. S., Polonsky, J. and Tingoli, M. (1979) J. Org. Chem. 44, 146. 9. Burfitt, I. R., Goodwin, T. E. and Wenkert, E. (1975) J. Org. Chem. 40, 3789. 10. Groven, S. H. and Stothers, J. B. (1974) Can. J. Chem. 52, 870. 11. Horeau, A. and Nouaille, A. (1971) Tetrahedron Letters 1939. 12. Garcia-Alvarez. M. C.. Paternostro, M. P.. Piozzi. F., Rodriguez,B,andSavona,G.(1979)Ph~tochemistr~lS, 1835. 13. Wahlberg, I., Almqvist, S-O., Nishida, T. and Enzell, C. R. (1975) Acta Chem. Stand. B29, 1047. B., Valade, J., Petraud, M. and 14. Delmond. B., Papillaud, Barbe, B. (1979) Org. Magn Reson. 12, 209.